This invention concerns an improved biocompatible and hemocompatible poly-(ether-urethane-urea) and a process for its preparation.
The need for suitable materials from which to fabricate prostheses such as cardiovascular and urinary tract implants as substitutes for damaged human and animal tissue continues to exist. Of special import is the need for a material other than autogenous tissue such as the saphenous vein to replace damaged veins and small diameter arteries.
Urethane elastomers, because of their excellent strength, tear, abrasion and oil resistance properties as well as their variety in structure, early found a large number of prosthetic uses. Of particular significance today are the linear block poly-(ether-urethane-ureas) in which a polyether diol is reacted with a diisocyanate and the resultant product is chain extended by reaction with a diamine. While such copolymers have been adapted for use in cardiovascular devices as described, for example, in U.S. Pat. No. 4,173,689, their sensitivity to discoloration in both the solid and solution form upon prolonged exposure to light and the tendency of solutions of the polymers to gel on standing limit their usefulness.
It is therefore a primary objective of the present invention to provide a modified poly-(ether-urethane-urea) which does not possess such shortcomings.